These days, in view of the problems related to the environment, copy paper is being reused much more than previously.
In general, after copy paper is used, it can be used as a raw material for recycled paper. In order to obtain a regenerated paper sheet from such a waste paper raw material, it was necessary to pulverize finely the waste paper raw material to a fibrous state, followed by applying paper making technology. Therefore, large facilities were required. Also, it was difficult to separate the developing agent from the paper. In addition, since the paper fiber was made shorter, it was necessary to use various additives such as a bleaching agent and an adhesive. Such being the situation, the regenerated paper sheet was not satisfactory in quality regardless of the recovery or recycling cost.
Under the circumstances, studies are being made in recent years on the use of a developing agent containing a pigment or a dye that brings about a decoloration reaction upon irradiation with light having a predetermined wavelength so as to achieve decoloration. In the case of using such a developing agent, the image formed on the copying paper sheet after use can be eliminated by simply irradiating the copying paper sheet with light, making it possible to use repeatedly the copying paper sheet without markedly degrading the paper sheet quality. Also, it is unnecessary to use large facilities and to mix various additives.
However, the light irradiation for a long time was required for sufficiently erasing the image formed on the used copying sheet, making it difficult to put the particular method into practical use.
One of the causes of the requirement of the light irradiation for a long time is that the irradiating light is attenuated before the irradiating light reaches the pigment or dye capable of decoloration and, thus, it is difficult for the irradiating light to reach a deep portion of the image formed on the used copying paper sheet.
The attenuation of the irradiating light is considered to be caused by the light absorption by the binder resin, the scattering of the irradiating light caused by the irregular surface of the image formed on the used copying paper sheet, the scattering and the absorption of the irradiating light caused on the surface of the developing agent, and the interface between the developing agents and the insufficient dispersion of the pigment or dye in the binder resin.
A first object of the present invention, which has been achieved in an attempt to overcome the above-noted problems inherent in the prior art, is to provide a developing agent capable of easily achieving the decoloration in a short time by simply irradiating the used copying paper sheet with light having a predetermined wavelength.
A second object of the present invention is to provide a method of manufacturing a developing agent capable of easily achieving the decoloration in a short time by simply irradiating the used copying paper sheet with light having a predetermined wavelength.
Further, a third object of the present invention is to provide a method of forming an image by using a developing agent capable of easily achieving the decoloration in a short time by simply irradiating the used copying paper sheet with light having a predetermined wavelength.
According to a first aspect of the present invention, there is provided a developing agent containing toner particles including a binder resin mainly containing an ethylene-norbornene copolymer and a coloring agent mainly containing a cyanine dye and an organic boron ammonium salt.
According to a second aspect of the present invention, there is provided a method of manufacturing a developing agent, comprising the steps of melting and kneading toner particle materials including a binder resin mainly containing an ethylene-norbornene copolymer and a coloring agent mainly containing a cyanine dye and an organic boron ammonium salt to obtain a kneaded mass; and pulverizing and classifying the kneaded mass to obtain toner particles.
Further, according to a third aspect of the present invention, there is provided a method of forming an image, comprising the steps of supplying a developing agent containing toner particles including a binder resin mainly containing an ethylene-norbornene copolymer and a coloring agent mainly containing a cyanine dye and an organic boron ammonium salt, onto an image carrier so as to develop the electrostatic latent image formed on the image carrier and, thus, to obtain a developing agent image; transferring the developing agent image onto a transfer material; and fixing the transferred developing agent image.
According to the present invention, an ethylene-norbornene copolymer having a high transparency is used as a binder resin, making it possible to permit the irradiating light to reach the coloring agent efficiently. As a result, it is possible to obtain a developing agent capable of an efficient decoloration by the light irradiation for a short time. The copying paper sheet having an image formed thereon by using the particular developing agent of the present invention can be decolored easily and, thus, can be reused promptly. It follows that the present invention permits realizing the saving of natural resources and a cost reduction.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.